Food Emulsifiers and Stabilizers - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 237

fortification with up to 16% soy flour and other protein-rich additives without loss
in the bread's physical properties. These would include an increase in water absorp-
tion and maximum hot-paste viscosity and volume, on crumb grain, and bread
softness. In reference to loaf-volume in breads, Finney 150 described the ability of
SE to (1) carry soy flour (protein), (2) spare shortening, and (3) strengthen dough,
i.e., improve gas retention with faster proofing. Sucrose monopalmitate was also
shown to be active in overcoming the volume-depressing effect of soy flour in
bread. 151 These authors concluded that sucrose monoesters were very good dough-
strengtheners. They showed that sucrose monolaurate and monopalmitate were more
effective dough strengtheners than either monocaprylate and monoarachidate. The
corresponding monomyristate, monostearate, and monooleate esters were almost as
effective as the monolaurate ester, but the monocaprylate ester was somewhat less
effective. These researchers also showed that the crumb-softening ability of sucrose
monostearate was effective, but not as effective as sodium stearoyl-2-lactylates, one
of the most widely used commercial bread softeners. The crumb-softening effect of
sucrose monoesters is diminished as the fatty acid chain decreases from C-18 to
C-8. Using surfactants, Tsen et al. 152 successfully made low-calorie cookies contain-
ing 25% shortening. In 1973-74, Tsen et al. 152,153 reported on the fortification of
wheat flour with soy flour to which several fatty acid derivatives, including sucrose
esters, fatty esters of polalkoxylated polyolglycosides, sodium or calcium stearoyl-
2-lactylate, and ethoxylated monoglycerides and glycolipids were added. Generally,
adding soy flour to wheat flour can produce adverse effects such as altered absorp-
tion, mixing, and machining properties, changed fermentation rates, poor crumb
grain and color, reduced loaf volume, and a beany flavor. However, addition of the
surfactants tested was found to eliminate many of these negative effects caused by
fortification of soy flour. Chung and co-workers 153 reported that SE with an HLB
value of 14 was very effective in replacing wheat-flour lipids and 3% shortening
while those with an HLB value of 1 proved ineffective. Ebeler and Walker 155 reported
that SE improved volume and softness of white layered cakes. SEs were subsequently
incorporated as emulsifiers in sponge cakes. 156 By hydrating SE prior to addition,
the resulting cake volume increased an average of 20 to 160 cc greater than when
SEs were added in the powdered form. The SEs with HLB values of 11 and 15 (the
more polar compounds) were the most effective.
NATURALLY OCCURRING EMULSIFIERS
P ROTEINS
Proteins are natural polymeric surfactants. The importance of proteins to food col-
loids and emulsions is reflected by the thousands of studies reporting their action at
various food interfaces. 157,158 This section will provide some general ideas and
characteristics of proteins as emulsifiers. Halling 158 claimed that proteins form high
viscoelastic films on surfaces which oppose the surface deformation (either in shear
or dilution) needed for the later stages of drainage and for the rupture of lamellae.
This theory faced considerable criticism as rheological interface properties depend
on other factors such as bulk protein concentration, pH, film age, etc. so that this